Glazing systems for curtain walls, storefront framing systems, and the like are known wherein a pressure plate retains a glazing panel in place against a frame member, such as a mullion. The mullions are anchored to the building and run between the floor slabs in a window wall application or past the floor slabs in a curtain wall application. Typically, a pair of gaskets is installed within grooves in the pressure plate, which is then fastened to the outer face of the frame member by screws. The gaskets bear against adjacent glazing panels, providing a seal against air and water leakage. A third gasket installed near the center of the pressure plate between the pressure plate and the frame member may also be utilized to provide an additional weather and thermal barrier, e.g., to prevent water and air from migrating from one side of the mullion to the other and providing a thermal barrier between the pressure plate and the mullion. This type of glazing system is labor-intensive to install, requiring multiple separate components to be assembled. Over time, the gaskets may shrink, compromising the integrity of the installation.
A co-extruded pressure plate made from polymer materials is disclosed in U.S. Pat. No. 5,592,795 as an alternative to the more common use of multiple separate gaskets with a metal pressure plate. In order for the pressure plate to be extruded integrally with the gaskets, it must be made of a material that is compatible with the elastomeric gaskets. It is challenging to utilize a compatible combination of currently available polymers for co-extrusion that have sufficient strength through the temperature extremes experienced by buildings for this application. Fiberglass pultrusions have been proposed for pressure plate applications to reduce thermal transfer, but are not as strong and or as easy to fabricate as aluminum pressure plates. Aluminum alloy pressure plates have desirable mechanical and manufacturing properties, despite having greater thermal conductivity. Aluminum provides the integrity and stiffness to maintain clamping pressure during all extremes of weather that are experienced by the exterior of a building. Alternative glazing systems to those presently known therefore remain desirable for different applications and requirements.